ES2748910T3 - Use of fluorinated alkene refrigerant compositions - Google Patents

Abstract

Use in a refrigeration system of a liquid composition comprising: a) a fluoroalkene of the structure: ** Formula ** where each R is independently Cl, F, Br, I or H; R 'is (CR2) nY; Y is CRF2; and n is 0; and b) an amount effective to provide lubrication of an essentially miscible organic lubricant comprising carbon, hydrogen and oxygen and having an oxygen to carbon ratio that provides a degree of miscibility with said fluoroalkene such that when up to five percent by weight is added of lubricant to said fluoroalkene the mixture has a liquid phase at at least a temperature between -40 and + 70ºC, and where the lubricant is selected from the group consisting of polyalkylene glycol, polyalkylene glycol ester, polyol-ester lubricants and vinyl ether; wherein the refrigeration system is selected from electric refrigerators, refrigerators, transport refrigeration systems and commercial refrigeration systems.

Description

DESCRIPTION

Use of refrigerant compositions of fluorinated alkenes.

FIELD OF THE INVENTION

The present invention relates to compositions used as refrigeration fluids in compression refrigeration systems, air conditioning, and heat pumps.

BACKGROUND OF THE INVENTION

The use of chlorine-containing refrigerants, such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and the like, as refrigerants in air-conditioning and refrigeration systems has come to be rejected due to the ozone-depleting properties associated with such compounds. As a result, it has become desirable to modify chlorine-containing refrigeration systems by replacing chlorinated refrigerants with non-chlorinated refrigerant compounds that do not deplete the ozone layer, such as hydrofluorocarbons (HFC's).

For any of the substitute materials to be useful in connection with refrigeration compositions, the materials have to be compatible with the lubricant used in the compressor. Unfortunately, many non-chlorine-containing cooling fluids, including HFCs, are relatively insoluble and / or immiscible in the types of lubricants traditionally used with CFCs and HFCs, including, for example, mineral oils, alkylbenzenes, or poly (alpha- olefins). For a coolant-lubricant fluid combination to work efficiently in a compression refrigeration, air conditioning, or heat pump system, the lubricant must be sufficiently soluble in the coolant over a wide range of operating temperatures. This solubility lowers the viscosity of the lubricant and allows it to flow more easily through the system. In the absence of such solubility, lubricants tend to lodge in the evaporator coils of the compression refrigeration, air conditioning or heat pump system, and in other parts of the system, thereby reducing the efficiency of the system.

Lubricating oils of polyalkylene glycol, esterified polyalkylene glycol, and polyol esters have been developed as miscible lubricants for coolants containing HFCs. Polyalkylene glycol cooling lubricants are described in U.S. Patent Nos. No. 4,755,316; 4,971,712, and 4,975,212. Polyalkylene glycol esters are described in U.S. Patent No. No. 5,008,028. Polyalkylene glycol and polyalkylene glycol ester lubricating oils are described as being miscible in fluoroalkanes containing one or two carbon atoms and free of double bonds.

As a consequence, fluorocarbon based fluids have found widespread use in the industry for refrigeration system applications, including air conditioning systems and also in heat pump applications, all of which involve compression refrigeration. Conversion cooling generally involves changing the cooling fluid from the liquid phase to the vapor phase by adsorption of heat at a relatively low pressure and then from the vapor phase to the liquid phase by subtraction of heat at elevated pressure.

While the primary purpose of refrigeration is to remove energy at a low temperature, the primary purpose of a heat pump is to provide energy at a higher temperature. Heat pumps are considered reverse cycle systems because for heating, the operation of the condenser is interchanged with that of the refrigeration evaporator.

The technique is continually seeking new pure fluorocarbon and hydrofluorocarbon based fluids that offer alternatives for heat pump and refrigeration applications. The Applicants have concluded that materials based on fluoro-olefins (fluoroalkenes) are particularly interesting because they possess characteristics that make them environmentally safer substitutes than the currently used fluoroalkanes (HFC's), which despite being safe for the ozone layer are suspected of causing global warming.

The Applicant has also come to recognize that HFC's refrigeration composition substitutes preferably possess in many cases certain behavioral properties to be considered acceptable substitutes, including acceptable refrigeration characteristics, chemical stability, low toxicity, non-flammability, lubricant compatibility and efficiency during use. The last characteristic is important in many refrigeration systems, air conditioning systems, and heat pump applications, especially when a loss in thermodynamic refrigeration behavior or energy efficiency can have secondary environmental impacts from the increased use of fossil fuels due to an increased demand for electrical energy. Additionally, it would be advantageous if the substitutes for HFC cooling compositions do not require fundamental technical changes from conventional vapor compression technology and lubricating systems currently used with HFC cooling liquids.

Flammability is another important property for many applications. Namely, it is considered important or essential in many applications, including particularly heat transfer applications, to use compositions that are non-flammable. Thus, it is frequently advantageous to use in such compositions compounds that are non-flammable. As used herein, the term "non-flammable" refers to compounds or compositions that are found to be non-flammable in accordance with ASTM E-681, dated 2002, which is incorporated herein by reference. Unfortunately, many HFC's that might otherwise be desirable for use in refrigerant compositions are not non-flammable. For example, fluoroalkane difluoroethane (HFC-152a) and fluoroalkene 1,1,1-trifluoropropene (HFO-1243zf) are both flammable and are therefore not viable for use in many applications.

Higher fluoroalkenes, that is, fluorine-substituted alkenes having at least 5 carbon atoms, have been suggested for use as refrigerants. U.S. Patent No. 4,788,352, to Smutry, is directed to the production of C5 to C8 fluorinated compounds having at least some degree of unsaturation. The Smutny patent identifies such higher olefins as known compounds that have utility as coolants, pesticides, dielectric fluids, heat transfer fluids, solvents, and intermediates in various chemical reactions. While the fluorinated olefins described by Smutny may have a certain level of efficacy in heat transfer applications, it is believed that such compounds may also have certain disadvantages. For example, some of these compounds may tend to attack some substrates, particularly general-purpose plastics such as acrylic resins and ABS resins. Additionally, the higher olefinic compounds described by Smutny may also be undesirable in certain applications due to the potential level of toxicity of said compounds that may occur as a result of the pesticidal activity indicated in Smutny. Also, such compounds may have a boiling point that is too high to make them useful as coolants in certain applications.

The Applicant has thus concluded a need for compositions, and particularly fluid transfer compositions, that are potentially useful in numerous applications, including vapor compression cooling and heating systems and methods, while avoiding one or more of the disadvantages indicated above. Furthermore, the Applicant has also recognized that the need for fluorocarbon-based and hydrofluorocarbon-based coolants that are environmentally safer than HFC's, possess similar or better characteristics with respect to at least certain thermodynamic cooling efficiency properties, persists in many applications, and they are compatible with existing lubricating systems.

JP 4 110 388 A describes heat transfer media for heat pumps and heat engines, comprising an organic compound represented by the molecular formula C ³ HmFn, where m is 1 to 5, n is 1 to 5, and m + n = 6 and that it has a double bond in the molecular structure.

US 5,053,155 A describes a 10% to 100% mixture of 1,1,2,2-tetrafluoroethane with at least one of 1,1,1,2-tetrafluoroethane and pentafluoroethane as a coolant mixed by a mono- or difunctional polyalkylene glycol Based on at least 80% propylene oxide having a SUS viscosity at 100 ° F (37.8 ° C) from 100 to 1200 is described for use in compression refrigeration.

EP 0.582.451 A1 describes a refrigeration oil composition for a fluoroalkane refrigerant, comprising a base oil composed mainly of an oxygen-containing compound and, based on the total weight of the composition, 0.005-5.0% by weight of a boron compound as an essential component.

The UNEP 2002 report of the Technical Options Committee on Refrigeration, Air Conditioning and Heat Pumps provides an overview of the refrigeration, air conditioning and heat pump industry following the implementation of the Montreal Protocol on Substances that Deplete the Ozone Layer.

Summary of the Present Invention

According to the present invention, the use in a refrigeration system of a liquid composition comprises:

a) a fluoroalkene of the structure:

wherein each R is independently Cl, F, Br, I or H; R 'is (CR2) nY; Y is CRF2; and n is 0; Y

b) an amount effective to provide lubrication of an essentially miscible organic lubricant comprising carbon, hydrogen and oxygen and having an oxygen to carbon ratio that provides a degree of miscibility with said fluoroalkene such that when up to five weight percent is added lubricant to said fluoroalkene the mixture has a liquid phase at at least a temperature between -40 and 70 ° C, and where the lubricant is selected from the group consisting of polyalkylene glycol, polyalkylene glycol ester, polyol ester and vinyl ether;

wherein the refrigeration system is selected from electric refrigerators, refrigerators, transport refrigeration systems and commercial refrigeration systems.

The fluoroalkenes of the present invention have been found to be miscible with existing polyalkylene glycol, polyalkylene glycol ester, and polyol ester lubricating oils. Therefore, in accordance with one aspect of the present invention, there is provided a liquid composition for use in electric refrigerators, refrigerators, transport refrigeration systems and commercial refrigeration systems in which a fluoroalkene of the structure:

wherein each R is independently Cl, F, Br, I or H; R 'is (CR ² ) nY; Y is CRF ² ; and n is 0;

it is combined with a sufficient quantity to provide lubrication of an essentially miscible organic lubricant selected from polyalkylene glycol, polyalkylene glycol ester, and polyol ester lubricants for electric refrigerators, refrigerators, transportation refrigeration systems, and commercial refrigeration systems.

Preferably, the fluoroalkene and organic lubricant mixture has a single liquid phase when up to 20% by weight of the lubricant is present in the mixture. Most preferably, the mixture is a single liquid phase in all proportions of the components of the mixture. This solubility or miscibility preferably exists at least at a temperature ranging from -40 ° C to 70 ° C, and more preferably essentially throughout the entire temperature range.

The present invention uses HFO's instead of HFC's which, despite being safe for the ozone layer, are suspected of contributing to global warming. At least some of the preferred HFO's according to the present invention have physical characteristics that allow them to replace HFC's with only minimal equipment changes.

Polyalkylene glycol lubricants suitable for use with the present invention generally contain from about 5 to 50 oxyalkylene repeating units containing 1 to 5 carbon atoms. The polyalkylene glycol can be straight-chain or branched, and can be a homopolymer or copolymer of 2, 3 or more oxyethylene, oxypropylene, oxybutylene, or oxy-ethylene groups or combinations thereof in any proportions. Preferred polyalkylene glycols contain at least 50% oxypropylene groups. The compositions according to the present invention may contain one or more polyalkylene glycols as the lubricant, one or more polyalkylene glycol esters as the lubricant, one or more polyol esters as the lubricant, or a mixture of one or more polyalkylene glycols, one or more polyalkylene glycol- esters and one or more polyol esters. Vinyl ethers are also useful in this invention.

Suitable polyalkylene glycols include the polyalkylene glycols of U.S. Pat. No. 4,971,712 and the polyalkylene glycols having hydroxy groups in each term described by U.S. Patent No. No. 4,755,316. The disclosures of both patents are incorporated herein by reference.

While suitable polyalkylene glycols include glycols that terminate at both ends with a hydroxyl group, other suitable HFO lubricants include polyalkylene glycols in which either or both terminal hydroxyl groups are protected. The hydroxyl group may be protected with alkyl groups containing 1 to 10 carbon atoms, alkyl groups of 1 to 10 carbon atoms containing heteroatoms such as nitrogen, the fluoroalkyl groups described by U.S. Patent No. No. 4,975,212, the disclosure of which is incorporated herein by reference, and the like. When both hydroxyl groups of the polyalkylene glycol are terminally protected, the same type or a combination of two different types of terminal protecting groups can be used.

Either or both of the hydroxyl groups may also be protected by formation of the ester thereof with a carboxylic acid as described in US Patent No. 5,008,028, the disclosure of which is also incorporated herein by reference. The lubricating oils in this patent are called polyol esters and polyalkylene glycol esters. The carboxylic acid may also be fluorinated. When both ends of the polyalkylene glycol are protected, either one or both ends may be protected with an ester, or one end may be protected with an ester and the other may not be protected or be protected with one of the alkyl, heteroalkyl or fluoroalkyl groups above mentioned.

Commercially available polyalkylene glycol lubricants include Goodwrench Refrigeration Oil for General Motors HFC-134a systems and Daimler-Chrysler's MOPAR-56, which is a polyalkylene glycol that is doubly protected by acetyl groups. Commercially available polyalkylene glycol esters include Mobil EAL 22 cc available from Exxon-Mobil and Solest 120 available from CPI Engineering Services, Inc. A wide variety of polyalkylene glycol lubricants are also available from Dow Chemical.

In preferred embodiments, the lubricants of this invention have viscosities ranging from about 1 to 1000 centistokes at about 37 ° C, more preferably in the range of from about 10 to about 200 centistokes at about 37 ° C and still more preferable from about 30 to about 150 centistokes.

In addition to the HFO refrigerant and lubricant, the compositions according to the present invention may include other additives or materials of the type used in refrigeration, air conditioning and heat pump compositions to improve their efficiency. For example, the compositions may also include extreme pressure and antiwear additives, oxidation stability and thermal stability enhancers, critical pour point and flocculation point depressants, antifoaming agents, other HFO's soluble lubricants, and the like. . Examples of such additives are described in U.S. Patent No. No. 5,254,280, the disclosure of which is incorporated herein by reference. The compositions of the present invention may thus include an amount of mineral oil lubricant that would not otherwise be miscible or soluble with e1HFO, but which is at least partially miscible or partially soluble when added to HFO in combination with a polyalkylene glycol, polyalkylene glycol -ester or polyol-ester. Typically, this is an amount of up to about 5-20% by weight. A surfactant can also be added to make the mineral oil compatible with polyalkylene glycol, polyalkylene glycol ester or polyol ester, and e1HFO, as described in U.S. Patent No. No. 6,516,837.

A wide range of methods for introducing the refrigeration compositions described herein into a compression refrigeration, air conditioning or heat pump system is described. For example, one method comprises connecting a refrigerant container to the low pressure side of a refrigeration system and starting the refrigeration system compressor to suction introduce the refrigeration composition into the system. In such methods, the refrigerant container can be placed on a scale so that the amount of refrigeration composition entering the system can be monitored. When a desired amount of the cooling composition has been introduced into the system, charging stops. Alternatively, a wide range of loading instruments are available commercially, known to those of skill in the art. Accordingly, in view of the foregoing description, those skilled in the art will readily be able to introduce the HFO refrigerant and the refrigeration compositions described herein into compression refrigeration, air conditioning and heat pump systems without excessive experimentation.

REFERENCE EXAMPLE 1

The coefficient of efficiency (COP) is a universally accepted measure of the efficiency of refrigerants, especially useful in representing the relative thermodynamic efficiency of a refrigerant in a specific heating or cooling cycle involving evaporation or condensation of the refrigerant in engineering refrigeration, this term expresses the ratio of useful refrigeration to the energy applied by the compressor in steam compression. The capacity of a refrigerant represents the volumetric efficiency of the refrigerant and provides a measure of the ability of a compressor to pump amounts of heat for a given volumetric flow of refrigerant. In other words, given a specific compressor, a refrigerant with a higher capacity will supply more cooling or heating energy. One means of estimating the COP of a refrigerant under specific operating conditions is to start from the thermodynamic properties of the refrigerant using standard refrigeration cycle analysis techniques (see for example, RC Downing, FLUOROCARBON REFRIGERANTS HANDBOOK, Chapter 3, Prentice-Hall , 1988).

A refrigeration / air conditioning cycle system is provided where the condenser temperature is approximately 150 ° F and the evaporator temperature is approximately -35 ° F under nominally isentropic compression with a compressor inlet temperature of approximately 50 ° F. The COP for various compositions of the present invention is determined over a range of condenser and evaporator temperatures and is reported in Table I below, based on HFC-134a having a COP value of 1.00, a capacity value of 1.00 and a discharge temperature of 175 ° F.

TABLE I

This example shows that some of the preferred compounds for use with the present compositions each have better energy efficiency than HFC-134a (1.02, 1.04, and 1.13 compared to 1.00) and the compressor that uses the Present refrigerant compositions will produce discharge temperatures (158, 165 and 155 compared to 175), which is advantageous since such a result is likely to lead to reduced maintenance problems.

EXAMPLE 2

The miscibility of HFO-1225ye and HFO-1234ze is tested with various cooling lubricants. The lubricants tested are mineral oil (C3), alkylbenzene (Zerol 150), ester oil (Mobil EAL 22 cc and Solest 120), polyalkylene glycol oil (PAG) (Goodwrench Refrigeration Oil for 134a systems), and a poly (alpha oil -olefin) (CP-6005-100). For each refrigerant / oil combination, three compositions are tested, namely 5, 20 and 50% by weight of lubricant, the rest being in all cases the compound of the present invention that is tested.

The lubricating compositions are placed in thick walled glass tubes. Vacuum is made in the tubes, the cooling compound according to the present invention is added, and the tubes are then hermetically sealed. The tubes are then placed in an environmental chamber with an air bath, the temperature of which varies from approximately -50 ° C to 70 ° C. At intervals of approximately 10 ° C, visual observations are made of the contents of the tubes regarding the existence of one or more liquid phases. In a case where more than one liquid phase is observed, the mixture is reported to be immiscible. In a case where a single liquid phase is observed, the mistura is reported as miscible. In cases where two liquid phases are observed, but occupying one of the phases only a very small volume, the mixture is reported to be partially miscible.

Polyalkylene glycol and ester oil lubricants were considered to be miscible in all proportions tested throughout the entire temperature range, except that in the case of HFO-1225ye mixtures with polyalkylene glycol, the coolant mixture was found to be immiscible in the temperature range was -50 ° C to -30 ° C and was partially miscible from -20 to 50 ° C. For 50 wt% concentration of PAG in the refrigerant and at 60 °, the refrigerant / PAG mixture was miscible. At 70 ° C, it was miscible from 5% by weight of lubricant in the coolant to 50% by weight of lubricant in the coolant.

EXAMPLE 3

The refrigerant compounds and compositions of the present invention are tested for compatibility at 350 ° C with lubricating oils of ^p A ^g while in contact with the metals used in refrigeration and air conditioning systems, which represents much more severe conditions than those found in many refrigeration and air conditioning applications.

Aluminum, copper and steel cutouts are added to thick walled metal tubes. 2 grams of oil are added to the tubes. The tubes are then evacuated and one gram of refrigerant is added. The tubes are placed in a 350 ° F (177 ° C) oven for one week and visual observations are made. At the end of the exposure period, the tubes are removed.

This procedure was performed for the following combinations of oil and the compound of the present invention:

a) HFC-1234ze and GM Goodwrench PAG oil

b) HFC1243zf and GM Goodwrench PAG oil

c) HFC-1234ze and MOPAR-56 PAG oil

d) HFC-1243zf and MOPAR-56 PAG oil

e) HFC-1225 and e and MOPAR-56 PAG oil.

In all cases, there is minimal change in the appearance of the tube contents. This indicates that the refrigerant compounds and compositions of the present invention are stable in contact with aluminum, steel and copper found in refrigeration and air conditioning systems, and the types of lubricating oils which are likely to be included in such compositions or used with such compositions in these types of systems.

COMPARATIVE EXAMPLE

Aluminum, copper and steel cutouts are added to a thick walled glass tube with mineral oil and CFC-12 and heated for one week at 350 ° C, as in Example 3. At the end of the exposure period, remove the tube and visual observations are made. The liquid contents are observed to turn black, indicating that there is severe decomposition of the tube contents.

CFC-12 and mineral oil have so far been the combination of choice in many refrigeration systems and methods. Thus, the coolant compounds and compositions of the present invention possess significantly better stability with many commonly used lubricating oils than the coolant-lubricating oil combination generally used in the prior art.

Claims (5)

1. Use in a refrigeration system of a liquid composition comprising: a) a fluoroalkene of the structure:

wherein each R is independently Cl, F, Br, I or H; R 'is (CR2) nY; Y is CRF2; and n is 0; Y b) an amount effective to provide lubrication of an essentially miscible organic lubricant comprising carbon, hydrogen and oxygen and having an oxygen to carbon ratio that provides a degree of miscibility with said fluoroalkene such that when up to five weight percent is added of lubricant to said fluoroalkene the mixture has a liquid phase at at least a temperature between -40 and 70 ° C, and where the lubricant is selected from the group consisting of polyalkylene glycol lubricants, polyalkylene glycol ester, polyol- ester and vinyl ether; wherein the refrigeration system is selected from electric refrigerators, refrigerators, transport refrigeration systems and commercial refrigeration systems. 2. Use according to claim 1, wherein the mixture has a liquid phase when up to 20 weight percent of lubricant is added to said fluoroalkene. 3. Use according to claim 2, wherein the mixture has a liquid phase in all proportions of fluoroalkene and lubricant. 4. Use according to claim 1, wherein the mixture has a liquid phase throughout the entire temperature range. 5. Use according to claim 1, wherein said fluoroalkene comprises 1,3,3,3-tetrafluoropropene.